Method of reducing corrosion



United States Patent 3,250,706 METHOD OF REDUCING CGRROSION Wayne Kuhn, Fishkill, N.Y., and Charles C. Nathan, Bellalre, Tex., assignors to Texaco Inc., New York, N.Y., a corporation of Delaware No Drawing. Fiied Aug. 30, 1963, Ser. No. 305,845 7 Claims. (Cl. 252-855) The present invention relates toa method of reducing corrosion of metal. One aspect of the invention pertains to the reduction of corrosion of metal apparatus in contact with petroliferous oil and gas well fluids and in contact with acidic compositions utilized in 'acidizing oil and gas wells. Another aspect of the invention relates to the reduction of the corrosion of metal subjected to acidizing treatments such as pickling.

In oil and gas condensate fields the production of petroliferous fluids from subsurface formations is often accompanied by extremely severe corrosion of metal appar-atus contacting the fluid produced. In some instances it is 'found that these fluids contain substantial amounts of organic acid materials such as acetic acid and/or carbon dioxide in the form of carbonic acid. These fluids are classified in the petroleum art as sweet. In other cases the fluids include corrosive sulfides such as alkali metal, and alkaline earth metal sulfides and hydrosulfides, hydrogen sulfide, .and/ or organic sulfides. The sulfide containing fluids are normally designated as sour.

Also in respect to oil and gas wells they are periodically subjected to an acidizing treatment in order to increase oil production. The acidizing solutions increase production by attacking and dissolving portions of the petroliferous fluid bearing rock thereby opening up new channels for the petroliferous fluid to flow through. The temperature at which acidizing is conducted is the temperature of the rock formation which may be as high as about 175 C. The acid treat-ing compositions normally comprise between about to 30 wt. percent aqueous solutions of strong acid such as sulfuric, hydrochloric, hydrofluoric, orthophosphoric, nitric, monofluorophosphoric, polyfluorophosphoric acid and organic acids such as acetic, abromopropionic acid and trichloroacetic acid. Hydrochloric acid and mixtures of, hydrochloric and hydrofluoric acids are usually employed. The acidizing solutions are, however, highly corrosive to the oil and gas well metal apparatus, e.g., ferrous metals such as steel and cast iron. In the absence of some method of retarding this corrosive attack the life of the oil and gas well equipment is materially shortened.

A corrosion problem closely related to that found in the aforedescribed acidizing treatment arises in the pickling of metals. Metal pickling can be defined as the removal of metal oxide from the surface of a metal structure by immersing said structure in a dilute mineral acid at a temperature ranging from ambient to about 90 C.

' The metals normally treated are the ferrous metals, copper, magnesium and the like and alloys thereof. The treatment is normally conducted with between about 5 to 80 wt. percent mineral acid such as sulfuric or hydrochloric acid. One of the problems as in the aoidizing treatment is to permit the acid to attack the oxide scale while inhibiting the acid attack of the metal itself.

We have discovered, and this constitutes the invention, that by incorporating a corrosion inhibiting amount of an alkyl (saturated aliphatic hydrocarbyl) substituted 1,2,3, 4,7,8,9,IO-octahydrophenanthridine in petroliferous oil and gas well fluids, oil and gas well acidizing solutions and acid pickling solutions the corrosion of metals in contact therewith is substantially reduced.

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The octahydrophenanthridine inhibitors contemplated herein are of the formula:

where R is an alkyl radical of from 5 to 10 carbons and R and R are selected from the group consisting of hydrogen and alkyl of from 1 to 5 carbons. Specific examples of the octahydrophenanthridine inhibitors of the invention are 6-pentyl-1,2,3,4,7,8,9,10-octahydrophenanthridine; 2,8-dimethyl-6-(3'-methylpentyl)-1,2,3,4,7,'8,9, 10-0ctahydrophenanthridine; 3,9-dimethyl-6-(4-methylpentyl)-l,2,3,4,7,8,9,10-octahydrophenanthridine; 1,7-dimethyl 6 (2'-methylpentyl)-1,2,3,4,7,8,9,IO-Octahydrophenanthridine and 2,8-dipropyl-6-(3' propylpentyl)-1,2, 3,4,7,8,9, 10-0ctahydrophenanthridine.

The octahydrophenanthridine inhibitors of the invention are prepared by contacting cyclohexanone, 2-alkylcyclohexanone, or 4-alkylcyclohexanone with ammonia at between about 300 and 400 C. in the presence of a thoria catalyst in a mole ratio of ammonia/cyclohexanone or alkylated cyclohexanone of between about 2:1 to 8:1. The alkyl portion of the alkylated cyclohexanones have from 1 to 5 carbons. cyclohexanone, 2-butylcyclohexanone and 4-propylcyclohexanone.

The alkyl-substituted octahydrophenanthridines employed in the method of this invention, as well as methods for their preparation, are disclosed and claimed in commonly assigned applications, Serial Nos. 356,061 and 356,064, filed March 31, 1964.

The octahydrophenanthridine inhibitor may be added to the petroliferous corrosive fluids in the ways known to the art. For example, if the inhibitor is to be applied to an oil well, gas well or pipeline, the octahydrophenanthridine may be added directly or as a solution in oil or other inert hydrocarbon solvents. In respect to oil and gas wells the inhibitor or solution is normally poured down the annular space between the casing and the tubing string. As to the pipelines the inhibitor can be injected at various points along the length thereof. The octahydrophenanthridine inhibitors need not be diluted. However, to insure a proper mixing solvent solutions containing 1 to 70 wt. percent of the inhibitor are properly employed. Although petroleum oils are the most economical diluent for the inhibitor, other diluents which are themselves oil soluble may be employed, for example, solvents such as kerosene, benzene, methyl alcohol, ethyl alcohol and isopropyl alcohol. In oil and gas petrolife'rous well fluid corrosion, although the amount of inhibitor combination employed in corrosive oil fluids is dependent on intensity of corrosive conditions and the degree of protection desired, normally between about .05 and 5 wt. percent of the inhibitor based on the corrosive well fluid mixture is utilized.

In respect to the oil and gas well acidizing solutions for producing formations the inhibitor is normally incorporated into the acidizing solution prior to the solutions introduction into the well. One method of introduction is simultaneously introducing separate streams of inhibitor and acid solution into the tubing in the well bore at the well head. To facilitate introduction of the inhibitor into the acid solution, inert diluents such as alcohols of the type and quantity described in relation to inhibiting petroliferous fluids may be employed.

Specific examples are Z-methyl- In regard to the pickling acid solutions the inhibitor is normally introduced directly into the pickling acid solution without dilution and the acid is agitated to insure inhibitor distribution therein.

The quantity of inhibitor utilized in the acidizing and pickling solutions is desirably between about .05 and 5 wt. percent.

The following examples further illustrate the invention but are not to be interpreted as limitations thereof.

EXAMPLE I This example illustrates the preparation of 6-pentyl- 1,2,3,4,7,8,9,10-octahydrophenanthridine.

.A glass reaction tube containing an 80 wt. percent thoria, wt. percent alumina catalyst was preheated to 350 C. while being swept with dry nitrogen. At 350 C. a stream of ammonia and cyclohexanone in a mole ratio of 4.721 was then passed through the tube at a residence time rate of 9.6 seconds. The gaseous product was condensed, collected and distilled. A water white viscous oil distillate fraction was analyzed by chromatography and determined to be 6-pentyl-1,2,3,4,7,8,9,10- octahydrophenanthridine having the following properties: Boiling point 170172 C. at 3 mm. Hg; density, C.=1.0071; refractive index, n =1.5455, n =1.5436

EXAMPLE II This example demonstrates the effectiveness of the novel inhibitor in suppressing corrosion of metals in contact with corrosive petroliferous oil and gas well fluids.

To a 4 ounce glass bottle there was added 100 milliliters (rnls.) of test mixture (oil-brine exposure fluid). The test mixture was prepared by combining 90 rnls. of

synthetic brine aqueous solution containing 10 wt. percent sodium chlorine and 0.5 wt. percent calcium chloride) and 10 mls. of an oil solution containing the octahydrophenanthridine inhibitor of Example I. The inhibitor was present in an amount to give the final 100 mls. mixture an inhibitor content of 1000 ppm. The oil used had a kinematic viscosity at 100 F. of about 4.5 centistrokes and an API Gravity of about 37. One ml. of a 6 wt. percent acetic acid was then added to the test bottle prior to sweetening or souring together with a weighed polished steel coupon. To simulate the sweet systems the fluid in the bottle was saturated with carbon dioxide gas at room temperature. Hydrogen sulfide was used as the saturating gas for simulating sour systems. In either case the bottle is then stoppered to maintain the carbon dioxide or hydrogen sulfide atmosphere. The stoppered bottle was then tumbled on a wheel for a period of 2 days at a temperature of about 155 F. At the end of the test period the test coupons are brushed, washed with acetone and water. dried and reweighed. For each test run a corresponding blank test run was made in which no inhibitor was employed.

In Table I below there is a compilation of corrosion test results:

Table I Test period, days Percent COI 'I'OS10!1 inhibition 1 Test conditions Sweet Sour 1 Bla.nk=0%. 1 Average of 3 test runs.

EXAMPLE III acid or an aqueous mixture containing 6 wt. percent hydrofluoric and 9 wt. percent hydrochloric acid. There was also added a weighed steel test coupon (P-l05 steel). The beaker was covered and maintained at a temperature of 100 C. for a period of 2 to hours. At the end of the test period the test coupon was removed, rinsed successively with water and acetone, dried and reweighed.

The inhibitor employed was the octahydrophenanthridine of Example I.

In the following Table 11 there is found a compilation of the corrosion data and test results:

This example further demonstrates the effectiveness of the inhibitor of the invention in reducing corrosion of metals in contact with acid treating solutions such as pickling solutions.

A weighed 70 mm. pure iron wire, British standard gage No. 24 was immersed for a 3.5 hour period in a stirred 7.5 wt. percent aqueous sulfuric acid solution maintained at 60 C. At the end of the 3.5 hour period the iron Wire was removed, washed with water and reweighed. Test runs were made in which the sulfuric acid pickling solution contained the octahydrophenanthridine of Example I. A blank run was also made in which no inhibitor was included in the pickling solution. The test data and results are reported in Table III:

1 Based on 7.5 wt. percent aqueous H2804 solution.

We claim:

1. A method of reducing the corrosion of ferrous metals comprising contacting said metals with a corrosive acidic solution selected from the group consisting of petroliferous oil and gas well fluid, acidizing solution for oil and gas rock bearing formations and metal pickling acid solution, containing a corrosion inhibiting amount of an octahydrophenanthridine of the formula:

where R is an alkyl radical of from 5 to 10 carbons and R and R are selected from the group consisting of hydrogen and alkyl of from 1 to 5 carbons.

2. A method in accordance with claim 1 wherein said corrosion inhibiting amount is between about 0.05 and 5 wt. percent.

3. A method in accordance with claim 2 wherein said 5 octahydrophenanthridine is 6 .pentyl 1,2,3,4,7,8,9,10- octahydrophenanthridine.

4. A method in accordance with claim 3 wherein said acidic solution is petroliferous oil and gas well fluid.

5. A method in accordance with claim 3 wherein said acidic solution is an acidizing solution comprising aqueous hydrochloric acid.

6. A method in accordance with claim 3 wherein said acidic solution is an acidizing solution comprising an aqueous mixture of hydrofluoric acid and hydrochloric acid.

7. A method in accordance with claim 3 wherein said acidic solution is a metal pickling solution comprising aqueous sulfuric acid.

References Cited by the Examiner UNITED STATES PATENTS 1,746,679 2/1930 Rhodes 252148 2,167,621 7/1939 Beaver 252-448 2,814,593 11/1957 Beiswanger et al. 252-8.55 2,955,083 10/1960 Levin 252-8.55

JULIUS GREENWALD, Primary Examiner.

H. B. GUYNN, Assistant Examiner. 

1. A METHOD OF REDUCING THE CORROSION OF FERROUS METALS COMPRISING CONTACTING SAID METALS WITH A CORROSIVE ACIDIC SOLUTION SELECTED FROM THE GROUP CONSISTING OF PETROLIFEROUS OIL AND GAS WELL FLUID, ACIDIZING SOLUTION FOR OIL AND GAS ROCK BEARING FORMATIONS AND METAL PICKLING ACID SOLUTION, CONTAINING A CORROSION INHIBITING AMOUNT OF AN OCTAHYDROPHENANTHRIDINE OF THE FORMULA: 